Arching mechanism

ABSTRACT

Arching mechanism, for instance for backrests of seats, medical or orthopaedic apparatus or casings and the like, with a pressure element wherein at least one traction element connected with a tensioning mechanism engages, which, when the mechanism is actuated can produce bulging by preserving a relative elevation of apex of the convexity; the arching mechanism can comprise a frame with inserted pressure elements actuatable by adjusting device(s), whereby frame segments are length-variable pressure elements; traction elements provided with tensioning mechanism can engage a slitted, overlapping or bellows-like bulging body for the opening and closing of these areas, which produces a curving of the bulging body in a predetermined direction or directions. (FIG. 1).

FIELD OF THE INVENTION

The invention relates to an arching mechanism, particularly for abackrest for a vehicle seat or seats for office and home furniture,respectively seats of all kind, as well as for use particularly inmedical or orthopaedic devices and apparatus, such as corsets or archsupports, in scaffoldings or casings, for the production of hulls, etc.

When for instance the arching of a backrest is adjusted, usually theapex of its convexity wanders according to the construction type of thearching mechanism over the height of the backrest, always remaining thesame. It does not adjust sufficiently to the constantly changingcurvature of a more or less curved spinal column, or to a stretching ofthe spinal column which is medically recommended or desired by the user.In constructions with shell seats, usually the lateral supportdiminishes with increased arching.

BACKGROUND OF THE INVENTION

The EU-B-37656 shows a restraining frame for a motor vehicle seat,wherein a support piece is suspended by springs. The support piececonsists of two lateral parts connected to the frame by springs andmutually connected by cross elements. There is a centrally locatedadjusting shaft which can be actuated by a hand wheel, the shaft runningthrough so-called engagement devices, which in turn are connected to theoutermost points of the lateral parts via flexible connection elements.When the hand wheel is turned, an arching of the support part issupposed to result, whereby basically in the beginning only an expansionof the springs occurs. This type of construction affords support to onlya few vertebrae; the vertebrae lying above and below do not get the samestrong support. A freely suspended insertion of the support part in thebackrest or a construction wherein the support is suspended in theupholstery is not possible.

The DE-OS 2804703 shows a backrest wherein a plate having strapsarranged oppositely to each other can be arched via mutually engagedguide rails. The entire plate is height-adjustable by means of a rockerlever.

The EU-A1-322535 shows a backrest with an upper and a lower supportstrap which are interconnected by a vertical, flexible strap and aspring tensioned between them, whereby an adjusting shaft engages via agear in the lower support strap, in order to achieve an arching of thebackrest by bending the flexible strap.

Further, backrests made of foam material are known, which are supposedto adjust to the shape of the spinal column.

Another example is shown by DE-OS 3440846 which discloses an automobileseat whose backrest comprises a frame and a plate received in the frame.The plate is provided with vertically extending longitudinal slits inwhich a lumbar-support device is movable. The lumbar support can beadjusted by a hand wheel through a shaft linked onto the frame to varyits stiffness and to move it vertically.

The lumbar support is directly connected with the frame. As a result,all vibrations imparted by the road to the vehicle are fully transmittedto the back of the driver.

The known mechanisms do not permit any accommodation to changed orchanging curvatures of the spinal column. For instance, during long cartrips, the curvature of the spinal column alters greatly as a result ofthe required holding work, when the total weight of the upper body mustbe supported based on this disadvantageous position (hand stretched outtowards the steering wheel). This muscle work, respectively holding workin order to keep the body upright under conditions of improper orinsufficient support has to be performed entirely by the musculature andthe skeletal system, and thus logically leads to considerableexhaustion, as well as muscle stress. The involved muscles require forthis work up to 40 times more blood, respectively 40 times more energy,compared to an anatomically supported upper body (whose muscles do nothave to perform any holding work).

The support, respectively holding work must be performed by the archingmechanism and namely for all spinal columns (whose curvatures are asvaried as human faces--and which in addition, are constantly alteredfrom hour to hour due to tiredness, exertion and the required holdingwork--the height of a person decreases from morning to evening beapproximately 2 to 4 cm, and the spinal curvature changes in this timeperiod by up to 10 cm). Thus, an optimal arching mechanism has to act ina differentiated manner so that for instance when used in a backrest, itcan suitably support any shape of back, i.e. at least threefold and withvariable strength, as follows: 1. very strongly and stably in forwarddirection in the pelvic area (against the backward tilting of thepelvis), 2. somewhat gentler but equally firm radially and vertically inorder to support each vertebra in the lower-back (lordosis) area and 3.essentially stronger and vertically in an upward direction in thepectoral area under the shoulders against the weight of the upper body.The additional support for the neck area can be a further requirement.

Once the arch is set and adjusted to the shape of the spinal column, itis naturally not allowed to change its shape even under fully exertedpressure, in order to insure full support independently from themomentary curvature of the spinal column of the user.

The at least triple support required from an ergonomically optimalbackrest can not be offered at all or only insufficiently by the knowndevices.

OBJECT OF THE INVENTION

It is therefore the object of the present invention to eliminate theabove-mentioned drawbacks and to create an ergonomically curvable andheight-adjustable arching mechanism with a wide spectrum of applicationand which, when used as a lordosis support, insures a multiple, at leasta triple support.

The invention solves the problem due to the fact that in the upperand/or lower region of the segment of the general pressure elementsupposed to be bulged, preferably at one of the transverse connectingmembers, engage one or more vertical traction or pressure elements,preferably a rod or wire, running in and/or parallel to the median axisof the general pressure element.

When the tension lock or the pressure mechanism is actuated, thecurvature caused by the mechanism occurs so that the apex of itsconvexity is maintained or is displaced with respect to its relativeelevation.

The relative position of the apex of convexity is thereby consideredeither with reference to the used frame, or a seat or even the apex ofthe lordosis of the person, i.e. when the person moves in the seatthereby altering the lordosis, the apex of the convexity of themechanism has still to remain always adjusted to the lordosis.

Another embodiment of the invention comprises a frame and thereininserted pressure elements actuatable by at least one adjustment device,preferably pressure strips or surfaces, and the vertically runningsegments of the frame are length-variable over at least one adjustmentdevice.

In a further embodiment variant of the invention, the arching mechanismcomprises an arching body, which is slitted, overlapping or shaped likebellows and at least at these points traction elements provided with oneor several tension mechanisms engage for closing, or opening of theseareas, whereby a curving of the arching body in each desired,preestablished direction can be achieved.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features and advantages of the presentinvention will become more readily apparent from the followingdescription, reference being made to the accompanying drawing in which:

FIG. 1 is an elevational view of an arching mechanism according to oneembodiment of the invention;

FIG. 2a is an elevational view of another mechanism for this purpose;

FIG. 2b is a side elevational view of the mechanism of FIG. 2a butshowing a bulging thereof in broken line;

FIG. 3 is a side elevational view of the mechanism of FIG. 1 showing thebulging thereof in broken line;

FIG. 4 is a view similar to FIG. 2a of still another mechanism accordingto the invention;

FIG. 5 is a side elevational view of the mechanism of FIG. 4 showing thebulged state in broken line;

FIG. 6 is a view of still another embodiment of the invention similar toFIG. 4;

FIGS. 6a, 6b are a fragmentary elevational view showing anotherarrangement of the cable of the embodiment otherwise shown in FIG. 6;

FIG. 7 is an elevational view of yet another embodiment of theinvention;

FIG. 7' is an end view of the embodiment of FIG. 7;

FIG. 7" is a side view of this embodiment;

FIGS. 8', 8" are an elevational view and side view of yet a furtherembodiment of the invention;

FIG. 8a is an elevational view, partly broken away of an embodimentsimilar to FIG. 8', showing a different handle arrangement;

FIG. 8b is a side view of the embodiment of FIG. 8a, a bulging or bowedconfiguration being represented in broken lines;

FIG. 8c is a view similar to FIG. 8a with a slight modification of thestructure thereof;

FIG. 8c' is a side view of FIG. 8c with the bowed state being shown inbroken lines;

FIG. 9 is an elevational view of a frame structure for a furtherembodiment of the invention;

FIGS. 9a-9e are used showing other actuating systems for the bowing ofthe device of FIG. 9;

FIG. 10 is an elevational view of yet another embodiment utilizing aneccentric drive for the bowing mechanism;

FIG. 10' is an end view of the embodiment of FIG. 10;

FIG. 10" is a side view of the embodiment of FIG. 10;

FIG. 11 is an elevational view of still another embodiment of theinvention, also using an eccentric to control the bowing of the frame;

FIG. 11' is an end view of the embodiment of FIG. 11;

FIG. 11" is a side view of the embodiment of FIG. 11;

FIG. 12a is a side elevational view of yet a further embodiment showingthe bowed state in broken line;

FIG. 12b is an elevational view of the embodiment of FIG. 12a;

FIG. 13 is a detail view of one eccentric arrangement for effecting thebowing;

FIG. 14 is an elevational view representing a detail of anothereccentric arrangement according to the invention;

FIG. 15 is a perspective view illustrating the bowing of another archingdevice according to the invention;

FIGS. 16, 16' are an elevational view and side view illustrating stillanother embodiment of the invention;

FIGS. 17, 17' are an elevational view and exploded view of yet a furtherembodiment of the invention;

FIG. 17' is an end view of this latter embodiment;

FIG. 17" is a side view of the embodiment of FIG. 17;

FIG. 17'" is a detail view of the connection of the cable or the deviceof FIGS. 17 and 17";

FIGS. 17"" is a detail view of another cable connection;

FIG. 18 is an elevational view diagrammatically illustrating a segmentalinstruction of the pressure elements which can be used in theembodiments previously described or subsequently described;

FIG. 19 is a diagram illustrating the principle of the inventionutilized in effecting bowing of various embodiments;

FIGS. 20, 20a are an elevational view, partly broken away, of mechanismfor applying tension to a cable as used in the invention;

FIG. 21 is an elevational view of yet another embodiment of theinvention;

FIG. 22 is a section taken along the line AA of FIG. 21;

FIG. 23 is an elevational view of yet another mechanism for effectingbowing of an arching mechanism according to the invention; and

FIG. 24, 24a are a view similar to FIG. 21 but illustrating yet anotherembodiment.

SPECIFIC DESCRIPTION

In FIG. 1, two vertically running and mutually spaced apart pressurerods 1, 1' are connected by transverse ribs 13, 13', runningperpendicularly thereto The upper end of the row of transverse ribsforms an end strip or slide strip 14, the lower end is formed by asupport plate 8 is provided on its outer edges with bores, whereinsprings 16, 16' are suspended, which again engage in a frame of thebackrest, not shown in the drawing.

In between and parallel to the two pressure rods 1, 1' starting from theend strip 14 down to the middle area of the arching mechanism, runs alocking or traction-assisting strap 9 in whose upper region a rod-liketraction element 2, e.g. for instance a bicycle spoke, is suspended. 1A'is the upper application point of the traction force. A further tractionelement 2' is suspended in the support plate 8 at B, which forms thelower application point of the traction force. The two traction elements2, 2' are further connected with a tension lock 3, arranged in thecentral area of the arching mechanism, which can be actuated via a handwheel fastened to the end of a shaft protruding from the archingmechanism.

When the hand wheel is turned, the mechanism starts to bulge (as shownby broken lines in FIG. 3), since both traction elements (2, 2') arepulled together.

FIG. 3 shows the path (h) between X1 and X2 travelled by the apex of theconvexity not dislocated from the original plane, during the arching orbulging of the mechanism or body.

In the embodiment of FIGS. 2a and 2b, the tension device is a bowdencable 10 having the traction element in the form of a wire running in asleeve. The upper and lower application points of the tension device onthe arching or bulging body are again marked A' and B'.

In the embodiment according to FIG. 4, the tension device is also abowden wire 10. The traction element 2" slidable within its sleeve bymeans of a screw drive, respectively a worm gearing 22, 23, is a wire,e.g. a bowden wire, engaging at the right side of the support plate 8.In the region at which wire exits the sleeve, the latter is connectedwith a further traction element. This traction element is a rod 2"',which is linked to the right-side area of a lever 7, which again isconnected via a short traction element with the locking-assisting strap.From the left edge of the lever 7, a traction rod leads to the left areaof the support plate 8. With this construction of the tension device, itis again possible to achieve a bulging of the entire mechanism bykeeping the apex of the convexity in place, since at the actuation ofthe wire line, the traction rod running outside on the left isentrained.

The embodiment shown in FIG. 6 is essentially based on the one shown inFIG. 4, but between the lever 7 and the end strip also a traction spring4 is provided and in the extension of this spring, between the lever 7and the support plate 8 a compression spring 5 is provided, wherebybetween the compression spring 5 and the support plate 8 a tighteningset screw 6 is provided.

The function of the lever can be taken over by a guide groove providedin the support plate 8, whereby the traction element designed as a wirecoming from the sleeve of the bowden wire runs over the groove, isredirected and runs up to the end strip, where it has a fixed end (FIG.6).

Corresponding to FIG. 4, from the point where the wire exits the sleeve10, a traction rod runs parallel thereto.

FIGS. 7, 7' and 7" show an embodiment of the arching or bulgingmechanism, wherein the pressure rods 1' are located at the extreme outeredge of the construction, forming the vertical segments of a frame. Thesupport plate for the pelvic edge is connected via a traction rod with alever which in turn, starting from its two ends, is connected on the onehand with a first traction-assisting strap and on the other hand, withthe sleeve of the traction wire of a bowden wire, whereby the cableengages in a second traction-assisting strap which is mirror-inverted tothe first, with respect to the center line of the construction.

FIGS. 8 and 8' show an embodiment of the arching mechanism with twoparallel, vertical pressure rods, with transverse ribs arrangedperpendicularly thereto and with a traction-assisting strap in thevertical median axis of the construction. On this traction-assistingstrap, a traction element 2"' is arranged, which is connected with atension lock 3 actuatable by a hand wheel. The outmost areas of thearching mechanism are connected to two traction springs 4, 4, which arelocated outside of the pressure rods and parallel thereto. The partsshown in broken lines show the position of the construction after abulging Instead of the tension lock 3', the actuation can also takeplace over a locking eccenter 17, 17' (FIGS. 8c8c').

According to another concept of the invention, the arching mechanismcomprises a frame whose vertical crossbars form the pressure elements.The frame is horizontally subdivided in two parts. As shown in FIGS. 9,9a, 9b, 9c, 9d, 9e, the mutually spaced-apart frame ends are eachconnected with a lever arm, whereby the respectively neighboring leversare interconnected and linked to traction elements. Furthermore, theends forming the open areas in the frame are each provided with a sleeveon each side of the frame.

As shown in FIG. 9a, each two neighboring levers are centrally connectedto each other, whereby each time the lower lever is connected via atraction element with the upper crossbar of the frame and the two upperlevers have a connection with the lower crossbar, wherein an adjustingdevice not shown in the drawing is interposed as an intermediary link.

When this adjusting device is actuated, the traction elements archprimarily the bulge at the outer edges of a for instance shell-shapedbackrest, whereby the pressure elements are subjected to an extension.Instead of pressure rods, it is also possible to use pressure surfaces.

This way, primarily an active bulge of the shell rim is created, wherebyinwardly arching transverse ribs (wires, straps, nets) are activelyarched in the area wherein also an arching of the shell is supposed totake place, due to the fact that they are entrained on their part, in afixed or springy manner, together with the two (or several) activearching edges of the shell. The shell shape of a surface remainsunimpaired by the intensity of the arching; the shell shape can even beemphasized. For instance, the bulging of a seating surface can beincreased, without thereby decreasing the depth of the shell.

FIGS. 10, 10' and 10" show a construction wherein the levers engaging atthe ends of the divided frame can also lead to an actuation device via atraction element. This arrangement comprises a disk plate centered onthe vertical centerline of the construction, which can be rotated bymeans of a handle. The handle can be fixed in notches (FIG. 10"). Thedisk plate has two almost circular, decentered, mutually offsetrecesses, each of them having one traction element leading to the lowerarea and one traction element leading to the upper area of the frame,this way forming a double eccenter. FIGS. 10' and 10" show the shape ofthe construction after the bulging process. The device for bulging theconstruction described in FIG. 10 finds use also in FIG. 11, howeverhere it is centrally inserted in the arching mechanism, whereby fromeach one recess of the eccenter two traction elements extend to theouter reaches of the frame, symmetrically to the vertical centerline.

The shape achieved after the actuation of the arching device is shown inFIG. 11".

The FIGS. 13 and 14 show for instance an eccentric disk actuatable via acable line or a rack-and-pinion combination, whereby the disk itself isdesigned as a toothed wheel.

FIGS. 12a and 12b show a lever connected to the lower support plate viaa spring, which lever is in turn connected via traction elements withthe upper, respectively lower regions of the arching mechanism and canbe fixed in notches after the corresponding bulging of the backrest(represented in broken lines).

FIG. 15 shows a combined construction, wherein the height as well as thebulge can be simply adjusted, whereby the traction elements marked "W"are responsible for the bulging and the traction elements marked "HV"are responsible for the height adjustment.

FIGS. 16 and 16a show an embodiment of the arching mechanism basicallyidentical to the one of FIG. 1, wherein however during bulging theentire mechanism slides along two rods symmetrically arranged withrespect to the vertical median axis.

The arching mechanism shown in FIGS. 1 to 24 can have further pressureelements (rods, surfaces, gratings, etc), which can be bulged indifferent directions, by providing for instance in one or several pointsinterruptions (open portions, overlappings) or locking straps or areassimilar to bellows (FIG. 18).

During traction, the traction elements used in such constructions, whicheither traverse the pressure elements or bypass them (possibly withinterposed spacers), due to the tension of one or several tensionmechanisms close the open, respectively overlapping interstices,respectively areas designed like bellows in the pressure elements, insteps or continuously. When using locking straps or other suitablemeans, the reinforced areas are in any case subject to either reduced orintensified bulging. Due to this aforementioned partial or completeclosing of the open portions or folds, a bulging occurs with respect tothe areas of the pressure elements which are not interrupted or designedlike bellows also in the direction transverse to the traction elements.Traditionally, a bulging surface can be arched only approximatelyparallel to or in the direction of the pressure elements. Due to this"multidimensionally" bulging construction, it is possible to obtain evenspherical or the like surfaces by closing the opposite open ends of aflat or slightly curved surface.

Such a construction type can be of use for instance in construction forcasing elements or in naval construction. The surface to be bulged, forinstance, can already be curved in advance by spring force and can bethen made to bulge in the same or in the opposite direction, by slightlyactuating the tension device. As a tension device for the archingmechanism according to the invention, it is possible to use also asimple cable winch, coil or bobbin, which can also serve for largerlength changes in the traction, respectively pressure elements.

It is also possible to use several arching mechanisms, whereby theireffects can be compounded or annihilate each other, so that for instanceone or several additional bulges in an already existing bulge can beachieved.

In this type of construction it is possible that--no matter which of thecooperating arching mechanisms are individually involved and in whichway--when the main traction element is relaxed all the individualarching units arranged to work together, against each other oroverlappingly, as well as the entire arching mechanism can be set tozero or to an intermediate or extreme value, and that when anotherarching process is started, only that part of the arching mechanismparticipates in the bulging, which according to the set slits, controllevers, eccentrics, etc and their lost motion areas (slits or other freespaces of the traction or pressure elements or of their articulations,stops, etc) are supposed to be actively arched (e.g. FIG. 19).

In the embodiment of the arching mechanism represented in this figure,it is possible to obtain any shape, from a minimal to a maximal bulge,depending on the position of the lever H (in broken lines or in stronglyextended position). Depending on the positioning of the lever H alongthe line IHV provided with direction arrows, an internal displacement ofthe apex of the convexity can take place (positions S1, S2, S3).

FIG. 20 shows a similar embodiment, wherein the variable archingpossibility of the arching mechanism and the internal height adjustmentoccur via a bowden wire, linear motor and modular system.

The arching mechanisms mentioned in the specification or also individualelements thereof can be manufactured in a construction assembly,respectively modular system and can be quickly assembled, replaced,repaired, and varied, respectively combined with any heretofore-known orfuture components or construction elements by using adequate connectionelements, e.g. elements like bicycle spokes with heads insertable incorrespondingly shaped bayonet-type fittings or the like or other plug,clip or clamp connections, etc. This modular construction type makespossible an individualized production of the mechanism, since allelements of the invention are selectively interchangeable with oneanother or can be integrated with already existing foreign elements(e.g. when the mechanism is built into an already existing seat oranother construction element). The arching mechanisms according to theinvention can replace the heretofore-used arching mechanisms or can bearranged in addition to the latter in selected angular positions orparallel in any desired combination.

The arching can be performed mechanically, electrically, pneumatically,and so on, directly or by remote control, and namely so that the apex ofconvexity can be height-adjusted at will or can be produced within theconstruction at will.

FIG. 21 shows an embodiment wherein the arching mechanism has beenintegrated in a backrest.

The backrest consists for instance of a U-shaped downwardly open frame27 and a frame crosstie 28. Inside this U-shaped frame, there are twovertically running tension wires 29, fastened to the frame. As shown inFIG. 21, these tension wires can be shaped for instance meander-like intheir upper portion. Also in the upper portion of the tension wires, afurther tension wire 29' runs horizontally through the backrest. In thelower portion of the two tension wires 29, which is basicallyrectilinear (but can also be offset to accommodate the gearing), a firstgearing 30 is provided, which can be mounted by means of clamp elements31. The first gearing 30 has a worm, a wormwheel and a pinion (all notshown in the drawing) connected to displace the first toothed rack 32.The toothed rack 32 is traversed in its lower area by a transverse shaft33. The gearing has a high transmission ratio, and thus the adjustmentof the support can be effected with small forces and low torque. Thepressure element is received by the tension wires 29, which also serveas slide wires, i.e. the pressure element is slidably arranged thereon.

The general pressure element is advantageously composed of an upper endstrip 34, mutually spaced-apart transverse ribs 35, 36, 37 and a supportplate 38 preferably arranged in the lower area of the backrest for thesupport of the pelvic edge of the spinal column, in this order. Theseelements are connected by at least two pressure strips 39 which areparallel to the tension wires. The upper end strip and the support plateare each slidably arranged on the tension wires by means of two slideeyes 40, 40' and 41, 41'.

The first gearing 30 is connected via a flexible shaft 42 with anelectromotor 43, arranged for instance in the lower area of thebackrest. When the first gearing 30 is actuated, a height adjustment ofthe general pressure element takes place. On the upper end strip 34, asecond gearing 44 is arranged, which equivalently to the first gearing30, is in working connection with a second toothed rack 45 via a hightransmission rate. This gearing is also driven by an electromotor 43'via a flexible shaft 42'. This second gearing is rigidly mounted to theupper area of the general pressure element Preferably, the two gearingare of identical construction and due to the reduced forces involved canbe made of plastic material. Preferably, the two gearings fastened byclamp elements 31 to the tension wires 29 can be simply mounted ordismounted. The two gearings are preferably made of plastic material,molded material, diecast metal or sheet metal.

The general pressure element does not necessarily have to be built inthe manner described above, for instance it can be made of one orseveral bulging plates of any pressure-resistant but flexible material,which again can be closed, perforated or grid-like or with a thicknessand resistance which varies in certain portions thereof, in order tomake possible the formation of different or identical curvatures indifferent areas.

In this embodiment, a triangular rocker lever 47 is articulated to thesecond toothed rack 45 by a pivot pin 46. The rocker lever has twobores, for instance one in its center and the other one in its endremote from the pivot pin. The left bore of the rocker lever shown inFIG. 21 is connected via rigid spoke 48 with the upper end strip 34 andover a further spoke 49 with the support plate 38.

When the second toothed rack is actuated, a curving of the pressureelement occurs, since the distance between the support plate and theupper end strip has to change, but the spokes remain rigid. Depending onthe curvature, the apex thereof wanders upwardly or downwardly. Theposition of the rocker lever (from slightly upwardly inclined toslightly downwardly inclined) depends on the selected degree of bulgingof the support.

Depending on the placement of the intermediate bore of the rocker lever,differing transmission ratios can be created. By modifying the length ofthe second toothed rack, the fulcrum formed by the pivot pin isentrained. If the distance of the bores is equally big, the spoke willcomplete only half the stroke compared to the second toothed rack(halved force equals double stroke).

Since the arching mechanism slides along the tension wires by means offour eyes, which can also be replaced by slide rings, it has provenparticularly advantageous to use snap elements for this purpose, forinstance open, especially U-shaped elements which narrow down towardsthe opening.

This way, the entire construction can be treated as a module and can bereplaced or mounted in seconds, during mounting or necessary repairs.The motors 43, 43' are advantageously mounted on the frame by means offastening brackets 50.

All or some of the individual elements "under tension" of theconstruction are kept at a distance with respect to the general pressureelement (or parts thereof) either for instance by the offset ends (51,52) of the general pressure element, as can be seen from FIG. 22 whichis a section along the line A--A in FIG. 21, or by separate spacingelements, respectively construction elements, or by a slightprestressing of the traction elements, etc., which determines thedirection of bulging. Further, an embodiment with a common drive is alsoconceivable.

A general representation of this variant can be found in FIG. 23.

A further embodiment, similar to the one shown in FIG. 21 is shown inFIG. 24. The drive of the arching mechanism takes place here over bowdenwires 53 and two linear motors 54, 54'. The linear motor 54 arranged inthe figure to the right serves for the direct, respectively indirectcontrol of the bulge.

A direct bulge control takes place then when the bowden wire engagesdirectly at the arching mechanism. The control shown in the drawingfigure which takes place via the transmission rocker lever 55 is anindirect control. This can also take place via guide rollers, curves,etc.

The control shown in the figure to the left represents a double-actinglinear drive 54', which on one side retracts the bowden control cable53' and on the opposite side relaxes the same cable. This way forinstance the height adjustment of the pressure element along the tensionor slide wires can be performed, but it can also be achieved on or inslide rails, in or on slide surfaces, in shell bodies or directly infree space, suspended on or hanging from one or several bowden wires.

The bowden-wire sleeve 56 guiding the bowden control cable 53' isattached on top and bottom to the guide wire by means of a suspendedeyelet spoke or directly to the frame (in points D, F, G). The movablebowden control cable or any other traction or control cable can now beclamped at selected points by means of one or several snap or screwconnections and fastened at a selected point (in this figure marked withthe possibilities A, B and C) via a control lever, or also over rods, ora cable winch, a thrust linkage, whereby at the displacement of the wireinside the bowden control wire or one of the aforementioned devices, thearching mechanism is synchronously moved together with the wiredisplacement. If the connection is made at the uppermost point (A) ofthe arching mechanism, during bulging, due to the shortening of theentire bulging surface, the apex of the convexity also wanders upwardlyexactly with the same percentage corresponding to the relation of thelengths between the upper edge and the apex, as well as the lower edgeand the apex.

First of all, this can be very important from the medical point of view,since in the base of a bulging for the "small-of-the-back archedposition" the person is also somewhat stretched.

If the fastening is done at the apex, the apex of convexity remainsconstant for instance with respect to the seat. In the case of aconnection at the lowermost point of the mechanism (C), during bulgingthe total length reduction resulting from arching becomes effective onlyat the uppermost end of the arching mechanism, and all other points, aswell as the apex of convexity are displaced downwardly, incorrespondence only to a percentage relation of the various length ofthe individual halves of the arching mechanism.

Naturally, the apex of convexity remains here unchanged, considered withrespect to the person, since the person becomes somewhat shorter whenthe spinal column is bent (the last mentioned embodiment suits thiscase) and the lordosis sinks thereby slightly downwardly.

Thus, each way of fastening depends primarily on the fact whether it isintended to synchronize the motion with the person. In an active backsupport, the apex of the convexity must be fixed. Then, the person canfind full support in the heightwise resting apex, when getting shorterdue to the arched back position. This way, the arching mechanism and notthe spinal column bears the weight of the upper body.

Further, it is conceivable to have a trailing or a forerunning phaseshift between the fixed apex of the lordosis and the apex of the archingmechanism, i.e. an overcompensation, respectively undercompensation ofthe apex takes place.

It is self-understood that the arching mechanism can be used in additionto other constructions or integrated in such constructions (for instanceattaching the mechanism to an already existing backrest). Further, itshould also be pointed out that the mechanism or elements thereof can bein connection with a memory, whereby bulging and apex position can beprogrammed and can be brought automatically in the selected positionwith the use of chips, magnetic cards, keys, etc. or the desired(required) bulge height, respectively apex point displacement can be setmechanically , e.g. with the aid of a four-way switch (tumbler).

As a result of this embodiment of the arching mechanism, wherein thecontrol unit is clamped with the bowden control wire and it is possibleto select at will the application point of this unit on the mechanism,preexisting conditions of the edges, such as hard or soft upholstery,various desired suspensions of the mechanism in a preexisting frame,etc. can be simply taken into consideration in any desired way, withoutjeopardizing the operation of the arching mechanism.

It is not only possible to over- or undercompensate the movements, butalso to take into consideration the respective seat constructions,upholstery materials, covers, suspensions, and so on.

The arching mechanism of the invention, described above with referenceto backrests, can of course be applied to many other fields, such asmedical or sports apparatus, toys, life-saving equipment, for variousprotective and carrying constructions, and so on.

We claim:
 1. An arching mechanism, comprising:a structure having a pairof opposite members movable toward and away from one another and a pairof parallel flexible resilient pressure members anchored to saidstructure and adapted to flex upon displacement of said opposite memberstoward one another to form an arch having an apex; a multiplicity ofelongated mutually parallel but mutually spaced apart transverseconnection members spanning across said pressure members and formingribs assuming a configuration of said arch; traction means including atleast one traction element interconnecting said opposite members andextending generally parallel to and along a median line through saidstructure for selectively drawing said opposite members toward oneanother; and means forming a tension lock connected to said tractionmeans and located between said opposite members and between saidpressure members, said tension lock includingmeans for actuating saidtraction element by application of arching force thereto to draw bothsaid opposite members simultaneously toward said tension lock and enableboth said opposite members to recede from said tension locksimultaneously, thereby selectively controlling convexity of said archso that said apex remains substantially stationary for all convexitiesof said arch, and means for locking said traction means in selectedpositions to retain a selected convexity of the arch, said tractionmeans comprising a respective traction rod connected to each of saidopposite members, said means forming said tension lock comprising arotatable member to which both of said rods are articulated, said meansfor actuating including means for rotating said rotatable member.
 2. Thearching mechanism defined in claim 1 wherein said means for rotatingsaid rotatable member includes a hand wheel.
 3. The arching mechanismdefined in claim 1, further comprising springs at corners of saidstructure suspending said frame as a backrest.
 4. The arching mechanismdefined in claim 1, further comprising slide means between saidconnection members and said pressure members enabling relative slidingof said connection members and said pressure members.
 5. An archingmechanism, comprising:a structure having a pair of opposite membersmovable toward and away from one another and a pair of parallel flexibleresilient pressure members anchored to said structure and adapted toflex upon displacement of said opposite members toward one another toform an arch having an apex; a multiplicity of elongated mutuallyparallel but mutually spaced apart transverse connection membersspanning across said pressure members and forming ribs assuming aconfiguration of said arch; traction means including at least onetraction element interconnecting said opposite members and extendinggenerally parallel to and along a median line through said structure forselectively drawing said opposite members toward one another; and meansforming a tension lock connected to said traction means and locatedbetween said opposite members and between said pressure members, saidtension lock includingmeans for actuating said traction element byapplication of arching force thereto to draw both said opposite memberssimultaneously toward said tension lock and enable both said oppositemembers to recede from said tension lock simultaneously, therebyselectively controlling convexity of said arch so that said apex remainssubstantially stationary for all convexities of said arch, and means forlocking said traction means in selected positions to retain a selectedconvexity of the arch, said pressure members being springs.